Ferrous alloys and articles



Patented Dec. 1 5, 1947 FERROUS ALLOYS AND ARTICLES Russell Franks and William 0. Binder, Niagara;

Falls, N. Y., asslgnors to Haynes Stellite Company, a corporation of Indiana No Drawing. Application May 9, 1946, 1

Serial No. 668,331,

20 Claims. (cl. 75-128) 7 This invention relates to ferrous alloys designed particularly for use in applications where great strength at very high temperatures is required.

The continued development of such devices as superchargers, gas turbines, jet propulsion apparatus and the like depends upon the production of workable metals and alloys that are strong at the high temperatures at which such devices operate. Although several alloyshave been proposed for use in high temperature applications, the utility of such alloys has been limited either because they are not hot-workable or machinable or because they become brittle upon continued exposure to elevated temperatures. One characteristic of highly alloyed ferrous metals which complicates the problem considerably is that as the ferrous solid solution is more heavily loaded with alloying materials to increase the high-temperature strength, the high-temperature stability tends to decrease so that upon prolonged heating the material becomes unduly brittle.

There is accordingly a need for hot-workable, machinable alloys having great strength and stability at highly elevated temperatures, and it is the prinicipal object of this invention to satisfy this need.

This object is achieved by the invention which comprises a new ferrous alloy containing certain proportioned quantities of nickel, chromium, cohalt, tungsten, and at least one metal selected from the group consisting of boron and aluminnm as the principal constituents, together with relatively minor though essential amounts of manganese, silicon, carbon and nitrogen. Molybdenum and the impurities commonly present in steels of good quality may also be present in the new alloy.

Specifically, the alloy of the invention contains by weight 15% to 25% chromium; 2% to 25% nickel; to 40% cobalt; up to 8% molybdenum; 0.5% to tungsten; an aggregate of 0.01% to 3% of at least one metal selected from the group consisting of aluminum and boron, the boron content not exceeding 1% and the aluminum content being. not less than 0.5% in the absence of boron; and up to 2% manganese, up to 1% silicon, up to 0.35% carbon, up to 0.25% nitrogen; and the remainder substantially all iron and incidental impurities. Somewhat more of the minor constituents than the upper limits just specified may on occasion he used; For instance, if excellent forgeability is not essential, the carbon content may be above 0.35%, up to say 1%. In general, for the best hot-workability, the

alloys of the invention should contain about 15% to nickel and 10% to 25% cobalt, and iron should be present in a proportion greater than the proportion of any other single element, the iron content being between about 25% and 55% of the alloy. At least 5% and preferably at least 10% iron should be present in any case. Boron preferably does not exceed 0.7%. In the absence of molybdenum at. least 7.5% tungsten should be present in the alloy. If molybdenum is present, a preferred range is 0.5% to 5% molybdenum.

Alloys within the foregoing composition ranges are readily forged, welded, and machined and, as has been demonstrated by test, have remarkably great strength and stability at high temperatures, for example, 1200 F. and upwards. Machine parts of the alloys may be designed to operate at high stress for long periods of time at 1500" F. and at lower stress for moderate periods at somewhat higher temperatures, for instance. The invention includes cast or hot-worked articles and welded articles for use at elevated temperatures and composed of such alloys.

A useful test for determining the suitability of metals and alloys for high temperature applications is the so-called stress-rupture" test. In this test, each of several samples of a given material is subjected to a measured tensile stress at a particular elevated temperature, and the time re-- quired for the sample to fail under these conditions of temperature and stress is noted. The data obtained are then plotted, using time and stress as abscissa and ordinate respectively. A curve is thus established for the material tested, showing for the selected temperature the time required to cause failure of the material when a particular stress is applied. Usually curves are established for several different temperatures, and from these curves can be predicted quite accurately the length of time the material can withstand failure at a given stress applied at a given temperature. This information is valuable for design purposes, especially if the material selected may be subjected to overheating, overloading, or both.

In the table results obtained on testing several alloys typical of the invention are set forth. In this series of tests, all of the specimens except the twelfth which was forged, were in the cast condition. The reported values were obtained On testing at 1500 F. and a stress of 20.000, 25,000, or 30,000 pounds per square inch as indicated in the table. The time in hours for the samples to fail under these conditions is given in the table.

Table Composition-Rcmoindcr Substantially all Fe gg g sg g Cl N1 C M0 W B N 0 A1 20,200 25,030 30,030

18. 4. 2O 4 4 0. 12 0. 04 0. 09 N11 320 N. '1. N. T. 18. 5 4 20 4 4 O, 12 0. 04 0. 27 N11 847 N. T. N. T. 18. 5 4 20 1 4 0. 21 0. [14 0.03 N11 1112 N. T. N. T. 18. 5 4 2O 4 4 0. 23 0. 04 0. 03 N11 295 N. T. N. T.

18. 5 4 20 2 2 0. 4 0. 04 0. 1. N11 232 N. '1. N. T. 18. 5 4 1 4 2 (1. 4 (1. 04 0. 08 N11 216 N. T. N. T. 18.5 4 20 2.3 2.3 0.42 0.04 .27 1 N. T. 18 N. T. 18. 5 4 2O 4 4 O. 47 0. 04 0. 12 N11 13 4 N. T. N. T.

18.5 18 2O 1 4 0.5 0.04 0.28 N11 1138 N. T. N. T. 18. 5 15 4 4 0. 5 0. 04 0. N11 1 4000 N. '1. N. T. 18. 5 4 20 4 4 0. 44 0. 04 O. 33 N11 1332 N. T. N. '1. 20 20 20 3 2 N11 0.15 0.15 1 203 N. T. N. T.

18. 5 4 4 4 0. 57 0. 04 0. 08 N11 2133 921 262 18 4 35 7. 5 3 0. 50 N. D. 0. (16 N11 N. T. 362 T. 18 4 35 8 8 0. 57 N. D. 0. 07 N11 N. T. 362 126 18 15 20 N11 10 0. 31 N. D. 0. 09 N11 N. T. 950 N. T. 18 4 35 N11 10 0. 52 N. D. 0.10 N11 N. T. 2236 750 20 20 20 N11 15 0. 41 N. D. 0. 08 N11 N. T. 1776 732 20 20 20 N11 15 0.60 N. D. 0. 12 N11 N. T. N. T 1543 18 20 3 10 0. 38 N. D. 0.38. N11 N. T. N. T. 1044 18 20 40 N11 15 0. 39 N. D. 0.14 N11 (270 hi. 40,000 1). S. 1.)

N0 failure. N. T.=No Test. N. D.=Not determined.

The data in the above table illustrate the remarkable high-temperature strength of ironchromium-nickel-cobalt alloys containing properly proportioned quantities of molybdenum, tungsten, and boron. The data also show the strengthening effect of increasing nickel and cobalt.

In addition to their strength at high temperatures the alloys of the invention possess other desirable properties. They are strong and have good ductility at ordinary room temperature. They may be hot-worked and machined, the alloys containing 10% to 25% nickel and 10% to 25% cobalt being particularly notable in these respects. Ihe same alloys also possess unusual corrosion-resisting properties inthat they exhibit substantial resistance to corrosive attack by both oxidizing and reducing media. Additionally, the alloys of the invention are weldable by any of the conventional welding methods including electric arc welding, oxyacetylene welding, submerged-melt electric welding and solid-phase pressure welding.

To ensure the attainment of the desirable characteristics of the alloys of the invention it is most.

important that the composition limits set forth be adhered to so that the alloying elements are present in the proper proportions. If the proportions of molybdenum, tungsten, and carbon be higher than the ranges given, the alloys suffer in hot-workability and weldability, welds made in such alloys lacking toughness and ductility. The deleterious effects of too high proportions of these, elements can not satisfactorily be ofiset by increasing the proportions of cobalt and nickel in the alloys. Too high a carbon content or too low proportions of molybdenum, tungsten, boron or aluminum have adverse effects on the high-temperature strength of the alloys. Accordingly, care should be taken that the composition limits described be observed in making these alloys.

If the alloys are intended for uses in which they will be exposed to temperatures not in excess of about 1350 F., compositions near the lower limits of the ranges given may be used, but if the alloys will be used Where exposure to temperatures above 1350 F. is probable, compositions near the upper limits of the ranges given should be employed.

For th fabrication of wrought articles for use at the latter temperatures an alloy containing 15% 1944, which in turn is in part a continuation of our application Serial No. 511,318, filed November 22, 1943.

We claim:

' l. A hot-workable alloy containing 15% to 25% chromium; 2% to 25% nickel; 10% to 40% cobalt; up to 8% molybdenum; 0.5% to 15% tungsten; 0.01% to 3% in the ag regate of at least one element selected from the group consisting of aluminum and boron, the boron content not exceeding 1% of the alloy and the aluminum content being notless than 0.5% in the absence of boron; up to 0.25% nitrogen; the remainder substantially all iron and incidental impurities.

2. A hot-workable alloy containing 15% to 25% chromium; 2% to 25% nickel; 10% to 40% c0- balt'; '7.5% to 15% tungsten; 0.01% to 3% in the aggregate of at least one element selected from the group consisting of aluminum and boron, the boron content not exceeding 1%. of the alloy and the aluminum content being not less than 0.5% in the absence of boron; up to 0.25% nitrogen; the remainder substantially all iron and incidental impurities.

3. A hot-workable alloy containing 15% to 25% chromium; 2% to 25% nickel; 10% to 40% cobalt; 0.5% to 5% molybdenum; 0.5% to 15% tungsten; 0.01% to 3% in the aggregate of at least one element selected from the group consisting of aluminum and boron, the boron content not exceeding 0.7% of the alloy, and the aluminum content being not less than 0.5% in the absence of boron; manganese in an efiective propon- Such articles may be either aneaoro tion up to 2%; silicon in an eflective proportion up to 1%; carbon in an effective proportion not exceeding 0.35%; up to 0.25% nitrogen; the remainder substantially all iron, the iron content being between 25% and 55 4. A hot-worked article which in its normal use is exposed to elevated temperatures, said article being composed of an alloy containing 15% to 25% chromium; 2% to 25% nickel; to 40% cobalt; up to 8% molybdenum; 0.5% to tungsten; 0.01% to 3% in the aggregate of at least one element selected from the roup consisting of aluminum and boron, the boron content not exceeding 0.7% of the alloy and the aluminum content being not less than 0.5% in the absence of boron; carbon in a proportion not greater than 0.35%; up to 0.25% nitrogen; the remainder substantially all iron and incidental impurities.

5. A hot-worked article which in its normal use is exposed to elevated temperatures, said article being composed of an alloy containing 15% to 25% chromium; 2% to 25% nickel; 10% to 40% cobalt; 7.5% to 15% tungsten; 0.01% to 3% in the aggregate of at least one element selected from the group consisting of aluminum and boron, the boron content not exceeding 0.7% of the alloy and the aluminum content being not less than 0.5% in the absence of boron; carbon in a'proportion not greater than 0.35%; up to 0.25% nitrogen; the remainder substantially all iron and incidental impurities.

6. A hot-worked article which in its normal use is exposed tp elevated temperatures, said article being'composed of an alloy containing 15% to 25% chromium; 2% to 25% nickel; 10% to 40% cobalt; 0.5% to 5% molybdenum; 0.5% to 15% tungsten; 0.01% to- 3% in the aggregate of at least one element selected from the group consisting of aluminum and boron, the boron content not exceeding 0.7 of the alloy and the aluminum content being not less than 0.5% in the absence of boron; carbon in a proportion not greater than 0.35%; up to 0.25% nitrogen; the remainder substantially all iron and incidental impurities.

7. A welded article which in its normal use is exposed to elevated temperatures upwards of 1200 F., said article being composed of an alloy containing 15% to 25% chromium; 2% to 25% nickel; 10% to 40% cobalt; up to 8% molybdenum; 0.5% to 15% tungsten; 0.01% to 3% in the aggregate of at least one element selected from the group consisting of aluminum and boron, the boron content not exceeding 0.7% of the alloy and the aluminum content being not less than 0.5% in the absence of boron; up to 0.25% nitrogen; the remainder substantially all iron and incidental impurities. v 8. A cast article which in its normal use is exposed to elevated temperatures. said article being composed of an alloy containing 15% to 25% chromium; 2% to 25% nickel; 10% to 40% cobalt; up to 8% molybdenum; 0.5% to 15% tungsten; 0.01% to 3% in the aggregate of at least one element selected from the group consistin of aluminum and boron, the boron content not exceeding 1% of the alloy and the aluminum content being not less than 0.5% in the absence of boron; up to 0.25% nitrogen; the remainder substantially all iron and incidental impurities.

9. An alloy containing 15% to 25% chromium; 2% to 25% nickel; 10% to 40% cobalt; up to 8% molybdenum; 0.5% to 15% tungsten; 0.01% to 0.7% boron; manganese in an effective proportion up to 2%, silicon in an effective proportion 6 up to 1%; carbon in an eifective proportion not exceeding 0.35%; up to 0.25% nitrogen; remainder substantially all iron.

10. An alloy containing 15% to 25% chromium;

2%'to 25% nickel; 10% to 40% cobalt; 7.5% to 1 tungsten; 0.01% to 0.7% boron; manganese in an eflective proportion up to 2%, silicon in an effective proportion up to 1%; carbon in an effective proportion not exceeding 0.35%; up to 0.25% nitrogen; remainder substantially all iron.

11. An alloy containing 15% to 25% chromium; 2% to 25% nickel: 10% to 40% cobalt; u to 8% molybdenum; 0.5% to 15% tungsten; 0.5% to 3% aluminum; manganese in an effective proportion up to 2%, silicon in an effective proportion up to 1%; carbon in an efiective proportion not exceeding 0.25%; up to 0.25% nitrogen; remainder substantially all iron.

12. A hot-worked article which in its normal use is exposed to elevated temperatures upwards of 1200 F., said article being composed of an alloy containing 15% to 25% chromium; 15% to 25% nickel; 10% to 25% cobalt; up to 8% molybe denum; 0.5% to 15% tungsten; 0.01% to 0.7% boron; carbon in a proportion not greater than 0.35%; up to 0.25% nitrogen; the remainder substantially all iron and incidental impurities.

13. A hot-worked article which in its normal use is exposed to elevated temperatures upwards of 1200 F., said article being composed of an alloy containing 15% to 25% chromium; 15% to 25% nickel; 10% to 25% cobalt; 7.5% to 15% tungsten; 0.01% to 0.7 boron: carbon in a proportion not greater than 0.35%; up to 0.25% nitrogen; the remainder substantially all iron and incidental impurities.

14. A hot-worked article which in its normal use is exposed to elevated temperatures upwards of 1200 F., said article being composed of an alloy containing 15% to 25% chromium; 15% to 25% nickel; 10% to 25% cobalt; 0.5% to 5% molybdenum; 0.5% to 15% tungsten; 0.01% to 0.7% boron; carbon in a proportion not greater than 0.35%; no to 0.25% nitro en: the rema nder substantially all iron and incidental impurities.

15. A welded article which in its normal use is exposed to elevated temperatures upwards of 1200 F., said article being composed of an alloy containing 15% .to 25% chromium; 15% to 25% nickel; 10% to 25% cobalt; up to 8% molybdenum;

0.5% to 15% tungsten; 0.01% to 0.7% boron; carbon in a proportion not greater than 0.35%; up to 0.25% nitrogen; the remainder substantially all iron and incidental impurities.

16. A welded article which in its normal use is exposed to elevated temperatures upwards of 1200' F., said article being composed of an alloy containing 15% to 25% chromium; 15% to 25% nickel; 10% to 25% cobalt; 7.5% to 15% tungsten; 0.01% to 0.7% boron; carbon in a proportion not greater than 0.35%; up to 0.25% nitrogen; the remainder substantially all iron and incidental impurities.

17. A welded article Which in its normal use is exposed to elevated temperatures upwards of 1200 F., said article being composed of an alloy containing 15% to 25% chromium; 15% to 25% nickel; 10% to 25% cobalt; 0.5% to 5% molybdenum; 0.5% to 15% tungsten; 0.01% to 0.7% boron; carbon in a proportion not greater than 0.35%; up to 0.25% nitrogen; the remainder substantially all iron and incidental impurities.

18. A cast article which in its normal use is exposed to elevated temperatures upwards of 1200 F., said article being composed of an alloy 1200 F.; said article being composed of an alloy containing 15% to 25% chromium; 2% to 25% nickel; 10% to 40% cobalt; 7.5% to 15% tung ten;

0.01% to 1% boron; carbon in a proportion not greater than 0.35%; up to 0.25% nitrogen; the

remainder substantially all iron and incidental impurities.

. 20. An article required to withstand corrosionin both oxidizing and reducing media, which article is composed of an alloy containing 15% to 25% chromium; 15% to 25% nickel; 10% to 2 cobalt; up to 8% molybdenum; 0.5% to 15% tungsten; 0.01% to 3% in the aggregate of at least one element selected from the group consisting of aluminum and boron, the boron content not exceeding 0.7% of the alloy and the aluminum content being not less than 0.5% in the absence of boron; up to 0.25% nitrogen; carbon in an efiective proportion not exceeding 0.35%; the remainder substantially all iron and incidental impurities.

RUSSELL FRANKS.

WILLIAM 0. BINDER. 

